Abnormal communication in a communication system that is used in controlling facility equipment such as air-conditioning equipment and lighting equipment includes abnormal communication at a physical layer level in which, due to the shape of the transmission waveform on a transmission path becoming distorted for some reason, it becomes impossible to maintain the contents of a signal that was generated by a terminal at the transmission source until that signal arrives at a terminal at the transmission destination. In order to identify the cause of this kind of abnormal communication on a physical layer level, and to restore the communication system, being able to acquire and analyze the waveform at the instant that abnormal communication occurs is desirable.
An oscilloscope is known as a typical device for acquiring and analyzing a transmission waveform. In a typically sold oscilloscope, the voltage level can be set as a condition for acquiring the transmission waveform, however, this condition is not necessarily related to abnormal communication. Moreover, abnormal communication often occurs irregularly, and it is difficult to predict the timing at which an abnormality will occur. Therefore, it is very difficult to acquire the transmission waveform at the instant when abnormal communication occurs, which places a large burden on a worker that is trying to deal with the abnormal communication.
As technology for reducing this burden, Patent Literature 1 discloses an abnormal communication detection apparatus that acquires the transmission waveform when abnormal communication occurs by detecting abnormal communication by analyzing received communication data according to the protocol of the communication system, and recording the transmission waveform before and after the time of occurrence of a trigger signal that is generated as a trigger indicating that abnormal communication was detected.
Moreover, Patent Literature 2 discloses a communication state analysis system that makes analysis of the communication state more efficient by making it possible to reproduce the communication state by storing received communication data together with the time of reception, and transmitting that communication data in accordance to the reception time.